Cho, Han-Gook Andrews, Lester Infrared Spectra of the Complexes Os←NCCH<sub>3</sub>, Re←NCCH<sub>3</sub>, CH<sub>3</sub>–ReNC, CH<sub>2</sub>Re(H)NC, and CHRe(H)<sub>2</sub>NC and their Mn Counterparts Prepared by Reactions of Laser-Ablated Os, Re, and Mn Atoms with Acetonitrile in Excess Argon Acetonitrile forms primarily N-coordination complexes (M←NCCH<sub>3</sub>) with Os and Re metal atoms, but these metal atoms produce exclusively methylidyne complexes (HCMH<sub>2</sub>X) in similar previous reactions with small alkanes and halomethanes. The Os complex increases on visible photolysis and dissociates partially on UV irradiation without the generation of other new products, whereas the Re complex converts to other products (CH<sub>3</sub>–ReNC, CH<sub>2</sub>Re­(H)­NC, and CHRe­(H)<sub>2</sub>NC) on photolysis. The primary formation of the N-coordination complex originates from its stability relative to that of the nitrile π-complex in these systems. The agostic interaction in the methylidene complex is apparently insignificant, and this rare observation of a methylidyne product with Re reflects that H migration in the isocyanide system is less favorable than those in the hydride and halide analogues. Experiments with Mn gave weaker counterpart product absorptions. Infrared Spectra;HC;halide analogues;UV irradiation;agostic interaction;H migration;counterpart product absorptions;CH;methylidyne product;methylidyne complexes;Mn Counterparts;Mn Atoms;Excess ArgonAcetonitrile forms;Re metal atoms;isocyanide system;metal atoms 2012-09-10